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Updated: Sep 29, 2025
Lignin Down-regulation of Zea mays via dsRNAi and Klason Lignin Analysis
Published on: July 23, 2014
Underlying mechanism of accelerated cell death and multiple disease resistance in a maize lethal leaf spot 1 allele
Jiankun Li1, Mengyao Chen1, Tianyuan Fan1
1State Key Laboratory of Wheat and Maize Crop Science, Collaborative Innovation Center of Henan Grain Crops, Center for Crop Genome Engineering, College of Agronomy, Henan Agricultural University, Zhengzhou, 450002, China.
Abstract:
Multiple disease resistance (MDR) in maize has attracted increasing attention. However, the interplay between cell death and metabolite changes and their contributions to MDR remains elusive in maize. In this study, we identified a mutant named as lesion mimic 30 (les30) that showed 'suicidal' lesion formation in the absence of disease and had enhanced resistance to the fungal pathogen Curvularia lunata. Using map-based cloning, we identified the causal gene encoding pheophorbide a oxidase (PAO), which is known to be involved in chlorophyll degradation and MDR, and is encoded by LETHAL LEAF SPOT1 (LLS1). LLS1 was found to be induced by both biotic and abiotic stresses. Transcriptomics analysis showed that genes involved in defense responses and secondary metabolite biosynthesis were mildly activated in leaves of the les30 mutant without lesions, whilst they were strongly activated in leaves with lesions. In addition, in les30 leaves with lesions, there was overaccumulation of defense-associated phytohormones including jasmonic acid and salicylic acid, and of phytoalexins including phenylpropanoids, lignin, and flavonoids, suggesting that their biosynthesis was activated in a lesion-dependent manner. Taken together, our study implies the existence of an interactive amplification loop of interrupted chlorophyll degradation, cell death, expression of defense-related genes, and metabolite changes that results in suicidal lesion formation and MDR, and this has the potential to be exploited by genetic manipulation to improve maize disease resistance.
Insights
A maize mutant, les30, exhibits suicidal lesions and enhanced resistance to fungal pathogens. This study reveals an amplification loop involving chlorophyll degradation, cell death, and metabolite changes, offering potential for improving maize disease resistance.
Area of Science:
- Plant genetics
- Molecular biology
- Crop science
Background:
- Multiple disease resistance (MDR) is crucial for maize but the underlying mechanisms involving cell death and metabolites are unclear.
- Understanding these interactions is key to developing disease-resistant maize varieties.
Purpose of the Study:
- To investigate the interplay between cell death, metabolite changes, and MDR in maize.
- To identify the genetic basis of a novel maize mutant with enhanced disease resistance and lesion mimicry.
Main Methods:
- Map-based cloning to identify the causal gene in the les30 mutant.
- Transcriptomics analysis to assess gene expression changes.
- Phytohormone and phytoalexin profiling in mutant leaves.
Main Results:
- The maize mutant les30, caused by a mutation in LETHAL LEAF SPOT1 (LLS1) encoding pheophorbide a oxidase (PAO), displays spontaneous lesion formation and enhanced resistance to Curvularia lunata.
- LLS1 is induced by various stresses.
- Lesion formation in les30 is associated with activated defense genes, overaccumulation of defense hormones (jasmonic acid, salicylic acid), and increased phytoalexins (phenylpropanoids, lignin, flavonoids).
Conclusions:
- A novel amplification loop involving interrupted chlorophyll degradation, cell death, defense gene expression, and metabolite changes contributes to lesion mimicry and MDR in maize.
- This discovered mechanism provides a potential target for genetic engineering to enhance maize disease resistance.
